Deficient visual performance can have a significant negative impact on a patient's quality of life, affecting, for example, ability to perform normal daily tasks, perform at school, and perform at work. One type of vision problem experienced by a substantial number of patients is poor night vision. The inability to see clearly under such low light conditions can make it difficult and/or dangerous for a patient to operate a motor vehicle at nighttime. Patients that are more likely to experience night vision problems include those suffering from night myopia, those with an equatorial cortical cataract, and those who have had surgery to insert an intraocular lens and/or underwent LASIK surgery. Exemplary symptoms of poor night vision include glare, halos, starburst, ghosting patterns, and/or poor depth perception.
Certain therapies have been described for improving visual performance. For example, the Bernstein Center for Visual Performance offers programs that utilize visual aids, such as puzzles, stereoscopes, and eye glasses, designed to improve visual performance. U.S. Pat. Nos. 6,730,065; 6,515,006; 6,420,407; and 6,291,498 describe the use of phentolamine to, for example, optimize pupil size in a patient. However, the need exists for additional compositions and methods that provide improvement in visual performance.
Despite this need, it is difficult to prepare stable, aqueous formulations of phentolamine salt forms without the use of a chelating agent, such as, disodium ethylenediaminetetraacetic acid (EDTA). U.S. Pat. No. 7,229,630 describes test results of various aqueous formulations containing phentolamine mesylate and states, for example, that the presence of a metal chelator is believed to be necessary to maintain stability of the formulation.
In view of the need for better formulations for administering phentolamine or a pharmaceutically acceptable salt thereof to the eye of a patient, research has been performed and the present patent application describes the surprising discovery of stable, aqueous ophthalmic solutions free of a chelating agent. The aqueous ophthalmic solutions free of a chelating agent can be used to administer phentolamine mesylate to the eye of a patient, and the aqueous ophthalmic solutions have demonstrated good stability upon storage.
Accordingly, the present invention addresses the aforementioned need for improved formulations that can be administered to the eye of a patient for improving visual performance, and the invention provides other related advantages.